1. Field of the Invention
This invention relates to a method and an apparatus for seeing a desired target address on a record medium, such as an optical disk or an optical card, on which the recorded data are divided into plural data blocks.
2. Description of the Prior Art
On an optical recording medium in the form of a disk, such as an optical disk or an opto-magnetic disk, spiral or concentric tracks are formed, with each track being divided into a plurality of sectors. On an optical recording medium in the form of a card, such as an optical card, each band-like record area is divided into plural record tracks. At the prescribed position in the recording block, such as at each sector or each recording track, there are formed identification signals, including error detection codes such as sync patterns, addresses or cyclic redundancy check codes (CRC), as a result of pre-formatting by the card or disk supplier or formatting preceding the start of use of the new disk. It is by the address information included in the identification signals that a random access can be made to the recorded data on the record medium.
The identification part of each block or sector in which are recorded these identification signals is also termed the ID part or the address part in the broad sense of the term. In the case of certain optical disks, for example, there are multiply written, for example three times, a unit of the identification information formed of: an address consisting of a track address, a sector address and an error detection code (EDC) for detecting address errors.
It has also been proposed in regard to, for example, optical disks that the cyclic redundancy check code be replaced by an error correction code in order to deal with the higher error rates associated with optical disks. When accessing a prescribed sector on such a disk for signal recording or reproduction, the pickup head movement is controlled while checking the current address through reproducing the identification signals. In reproducing the address, a decoding operation such as the aforementioned error detection or correction operation is executed. This results in a complicated decoding process for error checking at the time of address reading or reproduction. Above all, when the information unit is formed by multiple recording or writing, it becomes necessary to determine the address by using, for example, a majority logic procedure after error detection or correction of each information unit, with a resulting complication of the hardware or the decoding algorithm and prolonged computing time, thus presenting difficulties in achieving high speed accessing.